In a couple of photos posted to the publication’s Instagram, the supermodel sisters are seen posing in the same gold Versace dress on each of their individual covers. But the “fashion industry’s most in-demand sisters,” according to British Vogue, also got together for the closest — and debatably most controversial — photo shoot that they’ve done to date.

The photo that sparked the controversy depicts the sisters unclothed and intertwined with each other. Despite the magazine’s nonchalant attitude about the editorial picture, people are turning to social media to take issue with the picture.

From “weird” to “vile” and “wrong,” audiences have expressed their extreme opinions on Twitter. But why, exactly, is the photo so offensive to so many people?

Adolescent, child, and family psychologist Barbara Greenberg, PhD, tells Yahoo Lifestyle that the reaction has to do with incest taboos and that the particular imagery is associated with sexual relationships. Although Greenberg praises the expression of women who feel comfortable with their bodies, she understands the place where others’ feelings may be coming from.

“Many, many people are clearly going to be uncomfortable because of what they see as a sister relationship being sexualized, and that brings up the hot-button topic of incest,” she says. “The visual brings up the topic of incest.”

According to comments on British Vogue‘s Instagram post, a sexualized relationship is exactly what people are grasping from the photo — with some going so far as to say that the publication is exploiting the Hadid sisters. But this is not the first time that people have reacted to familial affection in this manner.

A number of celebrities have faced scrutiny themselves for innocent expressions of affection that are confused with sexual actions. From David and Victoria Beckham to Hilary Duff, pictures of the stars kissing their kids on the lips have been criticized. Again, Greenberg says that the visuals tap into the incest taboo, which will trigger a strong response.